Arrangement for determining the presence of an active element in a body of molten metal

ABSTRACT

An apparatus for monitoring the oxygen content of liquid metals. A tubular shield surrounds a standard reference electrode and has an open end in which there is sealingly arranged a solid electrolyte member which is electrically connected with the reference electrode and which projects in part from the open end. Measuring means is connected with the reference electrode as well as with the mass of molten metal whose oxygen content is to be monitored. Immersion of the projecting portion of the solid electrolyte member is the mass of molten metal results in establishing of a voltage differential between the reference electrode and the mass of molten metal which voltage differential serves as an indication of the proportion of oxygen in the molten metal.

United States Patent Inventors Appl. No.

Filed Patented Assignee Priorities Hanl-Jurgen Engell Stuttgart; Eberhard Schulte, Dortmund-Hombruch, both of Germany Oct. 14, 1966 Oct. 26, 197 l Hoesch Alttlengeaellachaft Dortmund, Germany Oct. 14, 1965 Germany June 25, 1966, Germany, No. P 15 98 559.8

ARRANGEMENT FOR DETERMINING THE PRESENCE OF AN ACTIVE ELEMENT IN A BODY Horsley AERE Report R 3427," United Kingdom Atomic Energy Authority, 1961, pp. 1- 6 & FIG. 2

Justin, 0.G.," vol. 659, p. 590. 6-10-52 Primary Examiner-T. Tung Atrorney-Michael S. Striker ABSTRACT: An apparatus for monitoring the oxygen content of liquid metals. A tubular shield surrounds a standard reference electrode and has an open end in which there is sealingly arranged a solid electrolyte member which is electrically connected with the reference electrode and which projects in part from the open end. Measuring means is connected with the reference electrode as well as with the mass of molten metal whose oxygen content is to be monitored. Immersion of the projecting portion of the solid electrolyte member is the mass of molten metal results in establishing of a voltage differential between the reference electrode and the mass of molten metal which voltage differential serves as an indication of the proportion of oxygen in the molten metal.

PATENTEDum 26 I97! SHEET 20F 4 PAIENTEDum 2s ISTI 3,616,407

SHEET 3 0F 4 ARRANGEMENT FOR DETERMINING THE PRESENCE OF AN ACTIVE ELEMENT IN A BODY OF MOLTEN METAL The present invention relates to an arrangement for determining the presence of an active element in a body of molten metal. More specifically, the invention relates to such an arrangement which is to serve for the determination of the presence of active oxygen. Known arrangements for determining the presence of active elements, and particularly active oxygen, hereafter designated "oxygen for convenience, are both relatively inaccurate and slow. The latter is an important detrimental factor in the metal-processing industry, because the treatment of molten metals on the one hand must be rapid and frequently cannot await the outcome of a slow-acting arrangement, and, on the other hand, the oxygen content in a mass of molten metal varies quickly so that the reading obtained with a slow-operating arrangement is frequently already outdated by the time the determination of oxygen has been made by the arrangement.

It is therefore a general object of the invention to provide an arrangement for determining the presence of an active element in a body of molten metal which provides quick readout of the quantity of the active element present in the molten metal.

A further object of the invention is to provide such an arrangement which is simple to manufacture and therefore inexpensive, and which is highly reliable in operation.

A further object of the invention is to provide such an arrangement which can be manufactured so inexpensively that its use is economically feasible even if the arrangement is to be utilized only for a single testing operation.

A concomitant object of the invention is to provide an arrangement of the type set forth above which is not influenced in its readings by ambient conditions.

In accordance with one feature of our invention we provide an arrangement for determining the presence of an active element in a body of molten metal, which arrangement comprises a standard reference electrode, a mass of molten metal which is spaced from the standard reference electrode, and a solid electrolyte which is partially located outside of the mass of molten metal and partially immersed therein. The solid electrolyte is electrically connected to the standard reference electrode. Our arrangement further includes means for determining the voltage differential between the mass of molten metal and the standard reference electrode which are electrically connected to one another by the solid electrolyte, and the voltage differential determined by this arrangement serves as an indication of the proportion of active element present in the molten metal.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings in which:

FIG. I illustrates an embodiment of the invention;

FIG. 2 is a partial detailed view of FIG. I in sectional elevation and on an enlarged scale;

FIG. 3 is a view substantially similar to that of FIG. 2 but showing another embodiment;

FIGS. 4a and 4b are views substantially similar to FIG. 3 but showing two further embodiments of the invention;

FIG. 5 shows yet an additional embodiment of the invention in a view similar to FIG. 3;

FIG. 6 shows a further embodiment of the invention; and 5 FIG. 7 is a partially sectioned detailed view showing still another embodiment of the invention.

Discussing now the drawings in detail, and especially FIG. 1 thereof, it will be seen that reference numeral 19 indicates a container, for instance a crucible, containing a mass of molten metal 2l covered with a layer 22 of slag.

A lance or holder 11 carrries a protective shield in form of an elongated tube 12 consisting of electrically insulating heat and fire-resistant material, for instance quartz. A solid-electrolyte plug 13 isreceived in the open front end of the tube 12 and extends outwardly therebeyond with a forward portion. The rearward portion of the electrolyte, which latter may, for example, consist of ZrO, stabilized with CaO, is so seated in the open end of the tube 12 that the interior of the tube is sealed against the intrusion of the'slag 22, the molten metal 21 and the gaseous phase above the metal. A metallic conductor, for instance, a platinum wire 14, is conductively connected to the inner portion of the solid electrolyte I3 and in turn is'connected with a further conductor 15. The conductor 15 extends upwardly through the tube 12 and through the holder II. and is connected with a measuring instrument 17. The latter is electrically connected with the crucible I9--and thereby with the molten metal 21 contained in the latter-through a continuation of the conductor 15 and a magnet I8 secured to the conductor and placed against the crucible 19.

A conduit is provided through which an oxygen-containing gaseous carrier 16 is introduced into the interior of the tube 12. This carrier constitutes, together with the platinum wire 14, a standard reference electrode.

The operation of the arrangement shown in FIG. 1 will be obvious from a consideration of the foregoing description and of the drawing. Immersion of the solid electrolyte "into the mass 21 of molten metal causes establishment of a voltage differential between the reference electrode 14/16 and the mass 21 of molten metal which acts as the main electrode. The voltage differential is measured by the measuring instrument I! and its magnitude is a function of the quantity of active element present in the mass of molten metal. Thus, the quantity of such active element can be determined immediately on immersion of the solid electrolyte 13 into the molten metal 2] by simply reading the indication of measuring instrument 17.

The detailed view of FIG. 2 shows the construction of the solid electrolyte I3 and its connection to the platinum wire I4 more clearly. The protective tube 12, which preferably but not necessarily consists of quartz as mentioned earlier, has an interior cross section which tapers in the direction to its open front end. The solid electrolyte I3 is contigurated as a substantially conical plug and it will be obvious that insertion of this plug through the tube 12 in the direction towsrdsthe open front end thereof will cause the plug to jam" in the open front end of the tube after a forward portion of the plug has passed outwardly beyond the open front end of the tube 12. The rearward portion of the electrolyte 13, that is the portion which is located within the tube 12, will seal the open front end thereof against the intrusion of f contaminants. Al is evident from FIG. 2, the rearward portion of electrolyte I3 is provided with an axial bore 23, preferably centrally located. The front end of the platinum wire I4 is, in the embodiment under discussion, doubled back upon itself by being passed in opposite directions through two axial bores of a ceramic body 24 and that portion of the wire l4 which extends forwardly beyond the body 24 is helically twisted.'This helically twisted portion 26 is introduced into the bore 23 of the solid electrolyte l3 and is frictionally retained. As is evident from the drawing, the rearward portion of the wire 14 passes through a guide tube 27 located within the protective tube 12. The wire 14 is spaced from the walls of guide tube 27 and it will be understood that the latter serves for introducing the oxygen-containing gaseous carrier 16 to the interior of tube I2. Obviously, the carrier 16 introduced through tube 27 will escape from tube 12 by passing upwardly through the latter and leaving it at the rear end thereof.

To guard against any possible accidental displacement of the solid electrolyte l3 rearwardly into the interior of tube 12, which would lead to the intrusion of contaminants into the latter and cause subsequent misreadings by influencing the potential of the standard reference electrode, spring means can be provided which permanently bias the solid electrolyte 13 into the open front end of tube 12. Such an arrangement is shown in FIG. 3 where a spiral spring 28 is located inwardly of the solid electrolyte l3 and bears with its opposite axial ends against the latter and a support member 28, respectively, it being understood that the support member 28' is suitably secured to the wall of tube 12.

FIGS. 4 and 4b show two modifications of the arrangement of FIG. 3. In the case of FIG. 4a the solid electrolyte is designated with reference numeral 32 and the protective tube is designated with reference numeral 31. Unlike the embodiment shown in FIGS. 1-3, however, the solid electrolyte 32 in FIG. 4a is of spherical configuration. It is secured in the open front end of tube 31 by being seated in an inner peripheral recess of tube 31. The embodiment of FIG. 4b difi'ers from FIG. 4a in that the solid electrolyte, which is here designated with reference numeral 32', is of ovoid configuration. It is secured in the open front end of the protective tube, here designated with reference numeral 31, in the manner already explained with reference to FIG. 4a.

The embodiment of FIG. shows yet a further possibility of securing the solid electrolyte in the open front end of the protective tube. The latter is here designated with reference numeral 33 and it will be seen that the solid electrolyte in this embodiment has been identified with reference numeral 34 and is substantially spherical. The protective tube 33 is largely closed at its open end except for a relatively small opening and the spherical part of the solid electrolyte 34 is located entirely within tube 33. The electrolyte 34 is provided with a protuberance 34 which extends through the opening of tube 33 and outwardly therebeyond. To firmly seat the electrolyte 34 against undesirable movement and also to seal the interior of the tube against the intrusion of contaminants, a fireproof material 36 surrounds the substantially spherical portion of the electrolyte 34 so that the same is embedded in this material.

Coming now to the the embodiment of FIG. 6 it will be seen that this differs to some extent from those previously described. The holder is here designated with reference numeral 61 and carries a releasable head 62. Holder 61 and head 62 are electrically connected by the coupling arrangement 63. A thermally resistant layer 64 surrounds both the holder 61 and the head 62.

The head 62 is provided with a hollow interior 66 which is filled with a gaseous medium. A U-shaped protective tube 67 of heatand fire-resistant and electrically nonconductive material is so embedded in the head 62 that one of its arms 671 communicates with the space 66 whereas the other arm 672 communicates with a channel 68 which extends through the head 62 externally of the space 66. The bight of the U formed by the tube 67 is provided with an opening through which a forward portion of a plug-shaped solid electrolyte 69 extends outwardly beyond the tube 67. The rearward portion of the electrolyte 69, that is the portion which is located within the tube 67, is connected with a wire 71, e.g. a platinum wire, which extends through the arm 672 of the tube 67 and through the channel 68 to the electrical coupling 63. The wire 71 is connected through the intermediary of the electrical coupling 63 with a measuring instrument (not illustrated but similar to that of FIG. 1) which is turn is connected through a conductor 73 and the electrical coupling 63 with a contact member 74 embedded in the material of head 62 in such a manner that insertion of the head 62 into a mass of molten metal causes submersion in the latter not only of the solid electrolyte 69, but also of the contact member 74, thus connecting the measuring instrument (not shown) with the mass of molten metal.

It should be understood that when the head 62 is immersed into the mass of molten metal, the gaseous medium in the space 66 expands and flows through the U-shaped tube 67. Obviously, it thus flows along the wire 71 and constitutes with the latter the reference electrode. The gaseous medium escapes through the channel 68 which communicates with an outlet 75 which, in the embodiment of FIG. 6, is shown to form pan of the electrical coupling arrangement 63.

Of course, the use of a U-shaped protective tube is not limited to an arrangement in which a hollow space is provided, containing a gaseous medium. It is also possible to introduce the gaseous medium in the manner shown in FIG. 1.

Coming, finally, to the embodiment shown in FIG. 7, which is rather schematic but is believed to be clear enough for those skilled in the art, it will be seen that the solid electrolyte 77 and the electrical contact 78 which establishes electrical connection between the mass of molten metal and a suitable measuring instrument, can be protected against damage and contamination prior to use of the invention arrangement. This is accomplished by providing them with a cover of material which will melt at or below the temperature of the molten metal so that the arrangement can, for instance, pass through an'upper layer of slag without registering any potential difference and will become actuated only when the cover 79 melts upon immersion in the actual mass of molten metal.

The advantages of the arrangement in accordance with the present invention, will be obvious. The solid electrolyte can be configurated in an extremely compact manner and its resistance to thermal and mechanical stresses is significantly increased by this compact configuration. It is relatively light and inexpensive to manufacture. The protective tube not only serves as a carrier for the electrolyte but also shields the same and the reference electrode so that the use of separate insulation is not required.

Different materials from those indicated above may be used for the electrolyte as well as for the protective tube. This is also true of the particular configuration selected for either and these are all considerations which will be dictated by the particular requirements encountered.

The securing of the electrolyte in the open front end of the tube can be accomplished in various different ways, as discussed earlier. This includes embedding of the solid electrolyte by partially melting the material of the tube and it includes, as already discussed, securing of the electrolyte by means of a separate fire resistant material. The latter arrangement is particularly advisable if the electrolyte used has a higher coefficient of expansion than the material of the tube since in this arrangement the electrolyte can be disposed within the tube with circumferential clearance relative to the latter.

lt will also be understood that the oxygen-containing carrier need not at the temperature of the molten metal be only gaseous; it can also be liquid. Furthermore, it is also not absolutely necessary in any of the embodiments to provide an inner conduit through which the medium is introduced into the protective tube, although this is advisable to obtain proper readings if the protective tube is substantially cylindrical and the medium is introduced from an end of the tube which is remote from that end in which the solid electrolyte is secured, since otherwise the medium may not reach the inner portion of the solid electrolyte.

Relative to the embodiment of FIG. 6 it still should be noted that the transverse securing of the solid electrolyte 69 in the bight of the U-shaped tube 67 eliminates the need for special precautions against undesired displacement of the electrolyte into the interior of the tube, since the electrolyte can be so configurated that its inner end will abut the wall of the tube 67 opposite the opening through which its front end extends outwardly beyond the tube. The various possible ways in which a thus-configurated electrolyte plug can be introduced into the tube 67 will be obvious to those skilled in the art.

Generally, although not necessarily, the electrolyte and the protective tube will have to be exchanged after one or two tests have been made. It is for this reason that a holder is advantageously provided to which the arrangement can be releasably secured.

It will be understood that each of 'the elements described above, or two or more together, may also find a useful application in other types of arrangements differing from the types described above.

While the invention has been illustrated and described as embodied in an arrangement for determining the presence of an active element in a body of molten metal, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desiredto be secured by Letters Patent is:

1. An arrangement for determining the presence of an active element in a mass of molten metal, said arrangement comprising, in combination, a support movable towards and away from the mass of molten metal; a tubular shield of an electrically insulating material resistant to destruction by the heat of the molten metal on contact therewith, said tubular shield being carried by said support and having an open rear end and an open front end remote therefrom; a solid electrolyte plug member sealingly received in said front end and including an outer portion projecting outwardly therefrom, and an inner portion; guide means in the interior of said tubular shield; standard reference electrodes means including an electrode wire extending through said guide means in electrically conductive connection with said solid electrolyte member, and means for circulating an oxygen-containing gaseous carrier into and out of said tubular shield through said guide means and said open rear end; and measuring means operative for determining the voltage differential which develops between said standard reference electrode means and the mass of molten metal in response to immersion of at least said outer portion of said solid electrolyte member in the mass of molten metal, whereby the thus determined voltage differential serves as an indicator of the proportion of the active element in the mass of molten metal.

2. An arrangement as defined in claim 1, wherein said electrode wire is platinum.

3. An arrangement as defined in claim 2, wherein said solid electrolyte member possesses high resistance to thermal and mechanical stresses.

4. An arrangement as defined in claim 3, l; and further solid electrolyte member consists in said ZrCl stabilized with CaO.

5. An arrangement as defined in claim 1; and further comprising biasing means arranged in said tubular shield and permanently biasing said solid electrolyte member in the direction toward said open front end.

6. An arrangement as defined in claim 1 and further comprising frictional means conductively connecting said electrode wire and said solid electrolyte member.

7. An arrangement as defined in claim 6 wherein said electrode wire has an end portion, and wherein said frictional means comprises threads provided on said end portion and a bore provided on said inner portion of said electrolyte located within said tube, said end portion of said wire being received in said bore and said threads establishing frictional engagement.

8. An arrangement as defined in claim 1, wherein said shield, reference electrode and solid electrolyte member constitute a unitary assembly.

9. An arrangement as defined in claim 1, wherein said tubular shield is of substantially U-shaped configuration and provided at the bight of the U with an opening facing said mass of molten metal, said solid electrolyte member being in part received in said opening sealing the same.

10. An arrangement as defined in claim 1, wherein said inner portion of said solid electrolyte member is embedded in the material of said shield. a

11. An arrangement as defined in claim 1, wherein said inner portion of said solid electrolyte member is provided with at least one bore extending in direction toward but tenninating short of said outer portions of said solid electrolyte member. r

12. An arrangement as defined in claim ll, wherein said bore is coaxial with said shield.

13. An arrangement as defined in claim I, and further comprising a cruciblefor containing the molten metal and conductor means electrically connecting said measuring means respectively withsaid standard reference electrode means and with said crucible, said conductor means comprising magnet means connected to said crucible.

14. An arrangement as defined in claiml; and further comprising a cover of a material meltable at the temperature of the mass of molten metal and surrounding at least said outer portion of said solid electrolyte member for. protecting the same from contamination until immersion in the mass of molten metal.

15. An arrangement as defined in claim 1, wherein said inner portion of said solid electrolyte member defines with an inner surface of said tubular shield adjacent said open front end an annular clearance; and a fireproof material surrounding said inner portion and completely filling said annular clearance. I

16. An arrangement as defined in claim 1, wherein said tubular shield is provided inwardly adjacent said open front end with an inner circumferential recess; and wherein said inner portion of said solid electrolyte member is of a configuration substantially complementary to said recess and sealingly received therein.

17. An arrangement as defined in claim 16, wherein at least said outer portion of said solid electrolyte member if of substantially spherical configuration.

18. An arrangement as defined in claim 16, wherein said electrolyte member is of substantially spherical configuration.

19. an arrangement as defined in claim 16, wherein said electrolyte member is of ovoid configuration.

20. An arrangement as defined in claim I, wherein said guide means comprises a tube extending with clearance through said rear end of said tubular shield toward but short of said plug member.

21. An arrangement as defined in claim 9, wherein said inner portion of said solid electrolyte which is located within said tubular shield has a face abutting against an inner surface portion of said tubular shield located opposite said opening, and said outer portion which is located outside of said shield constitutes a projection of said inner portion.

a s s a a 

2. An arrangement as defined in claim 1, wherein said electrode wire is platinum.
 3. An arrangement as defined in claim 2, wherein said solid electrolyte member possesses high resistance to thermal and mechanical stresses.
 4. An arrangement as defined in claim 3, wherein said solid electrolyte member consists of ZrO2 stabilized with CaO.
 5. An arrangement as defined in claim 1; and further comprising biasing means arranged in said tubular shield and permanently biasing said solid electrolyte member in the direction toward said open front end.
 6. An arrangement as defined in claim 1; and further comprising frictional means conductively connecting said electrode wire and said solid electrolyte member.
 7. An arrangement as defined in claim 6, wherein said electrode wire has an end portion, and wherein said frictional means comprises threads provided on said end portion and a bore provided on said inner portion of said electrolyte located within said tube, said end portion of said wire being received in said bore and said threads establishing frictional engagement.
 8. An arrangement as defined in claim 1, wherein said shield, reference electrode and solid electrolyte member constitute a unitary assembly.
 9. An arrangement as defined in claim 1, wherein said tubular shield is of substantially U-shaped configuration and provided at the bight of the U with an opening facing said mass of molten metal, said solid electrolyte member being in part received in said opening sealing the same.
 10. An arrangement as defined in claim 1, wherein said inner portion of said solid electrolyte member is embedded in the material of said shield.
 11. An arrangement as defined in claim 1, wherein said inner portion of said solid electrolyte member is provided with at least one bore extending in direction toward but terminating short of said outer portions of said solid electrolyte member.
 12. An arrangement as defined in claim 11, wherein said bore is coaxial with said shield.
 13. An arrangement as defined in claim 1; and further comprising a crucible for containing the molten metal and conductor means electrically connecting said measuring means respectively with said standard reference electrode means and with said crucible, said conductor means comprising magnet means connected to said crucible.
 14. An arrangement as defined in claim 1; and further comprising a cover of a material meltable at the temperature of the mass of molten metal and surrounding at least said outer portion of said solid electrolyte member for protecting the same from contamination until immersion in the mass of molten metal.
 15. An arrangement as defined in claim 1, wherein said inner portion of said solid electrolyte member defines with an inner surface of said tubular shield adjacent said open front end an annular clearance; and a fireproof material surrounding said inner portion and completely filling said annular clearance.
 16. An arrangement as defined in claim 1, wherein said tubular shield is proviDed inwardly adjacent said open front end with an inner circumferential recess; and wherein said inner portion of said solid electrolyte member is of a configuration substantially complementary to said recess and sealingly received therein.
 17. An arrangement as defined in claim 16, wherein at least said outer portion of said solid electrolyte member is of substantially spherical configuration.
 18. An arrangement as defined in claim 16, wherein said electrolyte member is of substantially spherical configuration.
 19. An arrangement as defined in claim 16, wherein said electrolyte member is of ovoid configuration.
 20. An arrangement as defined in claim 1, wherein said guide means compromise a tube extending with clearance through said open rear end of said tubular shield toward but short of said plug member.
 21. An arrangement as defined in claim 9, wherein said inner portion of said solid electrolyte which is located within said tubular shield has a face abutting against an inner surface portion of said tubular shield located opposite said opening, and said outer portion which is located outside of said shield constitutes a projection of said inner portion. 